CTL2 peptides identified by mass spectrometry in protein immunoprecipitated from leukocytes with anti–HNA-3a. Proteins were separated by sodium dodecyl sulfate–polyacrylamide gel electrophoresis and stained with Coomassie blue. Bands of interest were excised and processed for analysis by mass spectrometry as described in “Mass spectrometry.” CTL2 was identified in each of 3 independent studies with statistical significance (P < .0001; Supplemental data). The 7 CTL2 peptides identified (shaded text) spanned almost the entire length of the protein.